There’s a lot of conflicting information on in-sink garbage disposals. Many Canadian communities are banning them for environmental reasons, while other cities require them. So if you have a choice, should you use your kitchen garbage disposal? Garbage disposals have plenty of downsides. But the answer is, as with so many environmental questions, it depends.
Energy and Water
Compared to most household appliances, garbage disposals don’t use a lot of electricity. But if you are trying to cut your home’s carbon footprint, it’s better not to use any appliance that you don’t actually need. And there are other ways to deal with kitchen waste besides grinding them under the sink.
The average person uses between two and five gallons of water every time they use the garbage disposal. Besides wasting water, the wastewater generated has environmental repercussions. Food waste contains a lot of nitrogen. Wastewater treatment plants remove solids and organic matter from wastewater. But only a few facilities use advanced waste treatment techniques to remove nitrogen. Nitrogen, like phosphorus, can act like a pollutant. These nutrients that are so valuable to crops on land contribute to algal blooms that harm aquatic life once wastewater is released to natural bodies of water.
Money and Trouble
Even ground up, all that extra organic material in your pipes can cause blockages, especially if your pipes are old. (That’s the main reason garbage disposals were banned in New York City until 1997.) The smell of food in the pipes can even attract rats.
In communities with older wastewater treatment plants, as in some New Jersey communities, the additional solid material in the wastewater can strain the facility’s capacity. Newer wastewater treatment facilities are designed to handle the extra volume of waste generated by garbage disposals. But operating the full capacity of these larger facilities cost more money than processing a lower volume of material. People who are not connected to a sewer system can purchase septic-safe garbage disposals, but waste from garbage disposals fill the septic tank faster and can clog the drain field. In some places, legal requirements for the size of a septic system tank increase by 50% when a “garbage grinder” is installed.
Relative Environmental Impact
There are claims that garbage disposals are more sustainable than putting organic waste in the trash. Water-heavy food scraps increase emissions from garbage trucks. They also produce landfill gas (LFG) in the landfill. But there are no life cycle analyses available to quantify the relative impacts of organic waste in the landfill and the wastewater. As is often the case with environmental questions, the lesser of two evils depends on your specific circumstances.
Are you connected to the sewer, or do you rely on a drain field? How old are your pipes and how old is the treatment facility they flow to? Does that facility collect biosolids, and if so, what does it do with them? Where does your garbage go? If it’s a landfill, do they burn off captured LFG or use it to create renewable natural gas? The best-case scenario for food waste in the garbage is that it goes to a landfill that collects LFG and uses it to generate renewable energy. The best-case scenario for food waste you dump down the sink is that it gets treated and then composted and used as fertilizer.
The Best Option
While the choice between disposal methods is complex, it’s also a false dichotomy. The best method for dealing with any kind of waste is always to create less of it. Eliminating food waste will decrease your carbon footprint more than any disposal method. Composting, whether through a commercial program or your own backyard or countertop home composting system, is the best choice for any food waste you can’t prevent. If you use a kitchen disposal, only use it for foods that you can’t put in your curbside or home compost bin. Disposals have their own limitations, so use yours as designed to avoid plumbing problems, preventable damage, and frequent replacement of the machine, all of which are a waste of resources.